/* 标准盒模型 */
*{
    box-sizing: border-box;
}
body{
    display: flex;
    /* 垂直居中 */
    align-items: center;
    /* 水平居中 */
    justify-content: center;
    height: 100vh;
    overflow: hidden;
    margin: 0;
}
.container{
    display: flex;
    width: 90vw;
}
.panel{
    background-size: cover;
    background-position: center;
    height: 70vh;
    border-radius: 50px;
    color: white;
    /* 鼠标变手 */
    cursor: pointer;
    flex:0.5;
    margin: 10px;
    position: relative;
    /* 当某个元素属性发生变化时，过度的效果，包括属性名，过度时间，过度曲线，延迟时间四个参数 */
    transition: all 2s ease-in;


}
.panel h3{
    font-size: 24px;
    position: absolute;
    bottom: 20px;
    left:20px;
    margin: 0;
    opacity: 0;
}
.active{
    flex:5;
}
.active h3{
    opacity:1;
    transition:opacity 0.3s ease-in 0.4 ;
}